This invention relates to a process for preparing glass fibers and particularly to the application of a size to continuous filament glass fiber strand during the formation of the strand.
In the production of continuous filament glass fiber strands, a number of individual glass filaments are drawn from an electrically heated platinum alloy bushing containing a molten supply of the glass. The glass passes through tipped orifices in the bottom of the bushing and forms inverted cones of glass at the ends of the tips. Individual filaments are drawn from the cones of glass at a high rate of speed, i.e., 5,000 to 20,000 feet per minute and are grouped into a strand as they pass over a suitable guide. The strand is thereafter wound on a rapidly rotating forming package.
There is no twist in the strand as it is formed and an aqueous size composed of a dispersion of a binder, a lubricant such as detrinized corn starch and a vegetable oil is applied to the individual filaments prior to the time they are grouped into the strand and wound on the forming tube. In order to bond the filaments together and maintain the integrity of the strand, the forming size is deposited on the filaments to provide a level of forming size solids of about 0.7 to about 2 percent by weight based on the weight of the glass. The strand is wound on the tube with a slight traverse so that succeeding turns cross each other at an angle, rather than being parallel to each other so that the strand can be more easily removed from the tube.
A typical glass fiber sizing composition is disclosed in U.S. Pat. No. 3,227,192 which is a sizing composition used for sizing glass fibers which are to be subsequently woven into cloth. Usually, after the forming package is wound, it is placed in an oven to dry or allowed to air dry to reduce the moisture content thereof so that the strand on the forming package can be removed therefrom. After the forming package is dried, the strand is unwound onto a bobbin, the forming package and the bobbin being mounted on a twist frame. During the unwinding and rewinding step, a twist is imparted into the strand which provides integrity for subsequent processing.
When the twisted strand or yarn is to be used for textile applications as previously described, two standard processes are employed to prepare the yarn. A plurality of bobbins are mounted on racks. The end of each bobbin is threaded through a tensioning disc and through a plurality of guide eyes, over a separating comb and onto a beam which is a large cylinder. The plurality of yarn ends are wound on this beam in parallel. This process is known as beaming. The yarn on the beam is used for the warp of a textile glass fabric.
The weft of the textile fabric which is woven generally perpendicualarly into parallel twisted strands coming off the beam is supplied by a quill mounted on an apparatus which weaves the weft yarn into the warp yarn. The quill is a spool of small diameter which has the yarn thereon supplied by a bobbin produced as previously described.
After the fabric is woven, it is heat cleaned to remove the size and set the fibers in the fabric. This heating is conducted at a temperature of about 1200.degree. to 1400.degree. F. for 30 to 40 seconds and is sufficient to volatilize the solids and remove them from the fabric and to soften the glass fibers in the fabric to set them in their new position. This process is described in greater detail in U.S. Pat. No. 2,845,364.
Because the weft and warp of the fabric are composed of twisted strand of yarn, the filaments are compressed into the yarn by the twist. Thus, it is necessary to use a plurality of these strands or yarn ends per square inch to have an adequate fill to produce an acceptable fabric. It has been desired by the manufacturers of fabrics to have yarn having no twist so that after heat treatment the single filaments would dissociate from their compacted form and provide increased filling characteristics thus reducing the amount of glass necessary to produce an acceptable fabric. However, yarn without twist has great difficulty in undergoing especially the quilling operation without breaking or fuzzing because once the single filament breaks, it has a tendency to strip away from the strand thus forming fuzz balls and lint. A further advantage of utilizing a yarn without twist in weaving applications is that the yarn can be pulled directly from the inside of the forming package and wound on quills thereby avoiding the additional steps of transferring the yarn from the forming package to the bobbin. However, problems have been encountered in pulling the yarn from the forming package to the bobbin because the strands have a tendency to adhere to each other. Thus, when a package is end found, e.g., a single strand is pulled from the center of a forming package and unwinding is begun. During the pulling while being unwound the strand coheres to other portions of the strand and a large tangle is pulled from the center of the forming package, thus causing a shutdown of the winding operation of the quills.
The instant invention provides a sizing composition and a method of applying the sizing composition to glass fibers which enables untwisted yarns to be utilized in weaving applications. Further, the invention provides a strand which can be pulled from the inside of the forming package without cohering to other portions of the strand. Also, the invention provides an untwisted strand capable of being woven in its untwisted form with relatively little fuzzing or lint accumulation on the weaving equipment. Still further, the instant invention provides a textile fabric which can be efficiently coronized without any adverse effects on the surface of the fabric.
In accordance with the instant invention, the glass fiber sizing composition is provided which comprises a starch, a lubricant, a textile softener and a nonionic wetting agent. The nonionic wetting agents in the sizing composition are at a level of 100 to 150 percent by weight based on the weight of the lubricant.
The starch component of the sizing composition is typically an amylose starch mixture having an amylose content of about 35 to 45 percent by weight and formed by admixing approximately equal proportions of: (a) a high amylose starch fraction viz. one containing about 50 to 60 percent by weight of amylose with a greater portion of the remainder being amylopectin and (b) a water repellent, low amylose starch fraction viz. one containing about 20 to 30 percent by weight of amylose with the greater portion of the remainder being amylopectin.
The basic starch components of the amylose containing starch employed in the starch mixture can be derived from any starch sources including corn, wheat, potato, tapioca, waxy maize, sago, rice, hybrid starches, etc. Conveniently, however, the starch component having the high amylose content, viz. 50 to 60 percent by weight, is derived either from potato starch or a hybrid corn starch having over 50 percent by weight amylose and the starch component having the low amylose content, viz. 20 to 30 percent by weight, as derived from corn starch. The overall amylose content of the starch mixture can vary from 35 to 45 percent by weight based on total starch content.
The high amylose starch component preferably contains about 55 percent by weight of amylose with the remainder being amylopectin. The high amylose component can constitute from about 45 to 55 percent by weight based on total starch content of the starch mixture. Preferably the high amylose component constitutes about 50 percent by weight of the starch mixture. When the high amylose component is employed in amounts significantly in excess of 55 percent by weight, it becomes increasingly difficult to mix the two starch components especially in aqueous media and the viscosity characteristics are deleteriously affected. Moreover, the burnoff of the binder becomes more difficult and expensive.
The low amylose content starch component is a water repellent starch which preferably contains from 25 to 27 percent amylose with the remainder being amylopectin. Instead of pure starch, the low amylose content component can and preferably does contain cross-links. Thus, preferably the low amylose content component is a lightly cross-linked corn starch having an amylose content of from 25 to 27 percent by weight. The starch components provide the sizing composition with bulk and impart strand integrity to the sized glass fibers, thus diminishing the development of fuzz which can lead to strand breakage. The low amylose content component being of a viscous nature can also be used contributing to the nonmigratory nature of the sizing composition. The low amylose component constitutes from about 45 to 55 percent by weight of the mixture based on total starch content and preferably about 50 percent by weight thereof.
The term "starch mixture" as used herein is intended to be descriptive of the fact that a plurality of different starches each having different amylose content, are employed in the instant sizing composition and not to preclude the possibility of chemical interactiion between the starch molecules of each of the starch components. In fact, some chemical bonding can be present between the molecules of both the high amylose starch and the low amylose starch, and such starch mixtures possessing intermolecular bonding between the starch components are considered to be within the realm of this invention.
Also considered to be included within this invention are starch mixtures wherein the low amylose component and the high amylose component are lightly cross bonded to provide a weak knit, yet three dimensional composite starch network which is water soluble or water dispersible.
Textile softeners are employed in the sizing composition in amounts which are sufficient to provide softening action to the sized strands. Such amounts being for example 4 to 15 percent by weight of the said amylose containing starch derivatives and preferably about 10 percent by weight of the said amylose containing starch derivatives. Typical textile softeners are alkyl imidazoline derivatives such as described in U.S. Pat. Nos. 2,200,815, 2,267,965, 2,268,273 and 2,355,837 which are incorporated herein by reference and made a part hereof.
Cation X is an example of such a material wherein the alkyl imidazoline derivative is the reaction product of stearic acid, tetraethylene pentamine and acetic acid. Acid solubilized water dispersible stearic amides and anhydrous acid solubilized water dispersible lower molecular weight fatty acid amides as well as anhydrous acid solubilized polyunsaturated lower molecular weight fatty acid amides can also be used as a softener.
The nonionic wetting agents useful in the practice of the invention which give this sizing composition its advantageous characteristics as a nontwisted weaving yarn are those having typically a hydrophilic and a hydrophobic molecular structure at juxaposed ends of the molecules thereof. Examples of suitable nonionic wetting agents include polyalkylene derivatives of esters, fatty acids, fatty alcohols, fatty amides, alkyl phenyl ethers and other derivatives. A preferable nonionic wetting agent useful in the practice of the instant invention is polyethylene glycol 600 monolaurate which is shown to be effective in a range of 40 to 100 percent by weight based on the weight of the lubricant in the sizing composition.
The lubricants which are found to be useful in the practice of the invention are typically vegetable oils which have been hydrogenated. A typical vegetable oil would be hydrogenated cottonseed oil, hydrogenated corn oil, hydrogenated soybean oil and the like.
In addition to the lubricant, starch, textile softener and a nonionic wetting agent, other ingredients may be added to the sizing composition to impart properties which are known to those skilled in the art. Cationic agents which can be included in the sizing composition such as cetyl or stearyl monoamine hydrochloride or acetate, decylamine, hexadecylamine and secondary and tertiary derivatives of the same, for example, dodecyl methylamine and salts thereof. Quaternary ammonium compounds such as trimethylstearyl ammonium bromides and chlorides and generally any of the amine compounds which dissociate in aqueous systems to provide a positive radical containing a group of more than 10, preferably 12 or more carbon atoms can be employed. These materials are cationic active substances.
A fungicide, such as one of the metalo-organic quaternary type, e.g., tributyltin oxide can be employed in sufficient amount to prevent mold attack on the amylose containing starch derivatives. Suitable effective amounts of the fungicide are about 3 milliliters to 75 gallons of the sizing composition.
Plasticizers can be employed in the sizing compositions to lessen the brittleness of the strand and to improve the end finding thereof. Carbowax 300 is a polyethylene glycol with an average molecular weight of 300. Further, polyethylene glycol is believed to impart even tension properties to the sized strand.
If desired, polyethylene glycol can be employed in conjunction with a water soluble polyvinyl alcohol in the size. This is often desirable because of the added film strength properties which sizing compositions containing this combination impart. The ratio of polyvinyl alcohol to the polyethylene glycol when used in combination ranges from about 1 to 1 to 2 to 1. The combined amount of polyethylene glycol and polyvinyl alcohol in the size is about 0.1 to about 0.2 percent by weight of the amylose containing starch component.
In place of the low molecular weight polyethylene glycol, glycerine can be employed in similar weight concentration, either alone or in admixture with polyvinyl alcohol. For most purposes however, the use of polyethylene glycol is preferred since it is less hygroscopic than glycerine.
Typically, the overall solids content of the size can vary from about 4 to 8 percent by weight. It should be noted that the solids content can be adjusted in accordance with the desired solids content for the specific forming conditions employed. Generally, the solids content will range from 5 to 7 percent by weight and preferably from 6.3 to 6.7 percent by weight. By solids content is meant the residual solids remaining after drying the sizing composition at 105.degree. C. to constant weight. The invention will be ellucidated by its further description in the following examples.